The present invention relates to a non-penetrating anchoring system for a roof membrane used to prevent moisture from entering a structure such as a building.
For many years, roofs were of the conventional built-up type, in which multiple layers of material, including a felt material soaked with bitumen, were used. Gravel was imbedded in the bitumen as the upper, exposed layer and was ballast to hold the layers of material down against being lifted by the wind.
In more recent times, an alternate roofing system has gained dominance, which is known as the "single-ply" roofing system. The single-ply roofing system includes the application of a suitable elastomeric membrane over a substrate. The substrate may be either rigid or non-rigid. Rigid substrates include concrete, corrugated steel, gypsum, plywood, and various types of insulation boards. Insulation boards include wood fiber board, perlite board, fiberglass with binder, urethane, urethane with composite of fiberboard perlite or fiberglass, polystyrene, cellular glass and cork board. Non-rigid roofing materials include batt or blanket types of insulation, which is compressible, as by a fastener which penetrates the insulation, or by a membrane which is placed over the insulation.
The membrane may be made of various selected materials, including chlorinated polyethylene, ethylene propylene diene monomer, chlorosyfonated polyethylene, modified bitumen, neoprene, polyisobutylene and polyvinyl chloride. These materials are generally produced in sheets which are transported in rolls having widths which range from about four feet to as much as fifty feet. And the length of the roll may be as much as 150 feet.
The membrane must not only be waterproof but must be prevented from being lifted by wind forces. A waterproof membrane construction is achieved by laying the membrane sheets on the substrate, lapping one over the other, and providing a joint at the overlap which is waterproof and moisture proof. Also, flashing in one form or another is utilized at the edges of the membrane, at pipes, etc.
The retention of the membrane on the roof substrate is achieved in several different ways. One is by a loose laid ballast system, in which small stones are placed over the membrane to hold it down. Another is the partially attached system in which the membrane is secured to the substrate in a distinct grid or geometric pattern. An example of a partially attached system is the "point attachment" construction in which spaced anchors are each secured by a linear fastener to the roof structure. The fastener may penetrate the membrane or may be part of a construction referred to as "non-penetrating". There are also known a totally adhered system, in which the entire undersurface of the membrane is adhered by a suitable adhesive to the substrate, as well as a so called protected membrane roof, which provides for insulation over the membrane.
In the point-attached single-ply anchoring systems there are several problems which must be overcome in both the penetrating and non-penetrating point attachment constructions. In some instances, the anchors have become detached from the roof, and it has now been discovered that this has resulted from a threaded linear fastener having "backed out" from its engagement with a nut or other threaded structure. There has resulted from this a reduction in integrity of the roof, including leakage and an increase in the risk of a roof blow off. Retrograde movement of the linear fastener has been found to be the result of vibrations caused by wind forces on the membrane.
Another problem associated with the non-penetrating construction is that the final locking element of the anchoring system may "pop out" or "snap off", thereby freeing the membrane, and significantly increasing the risk of a roof blow off.
One widely used non-penetrating point attachment construction has a base member with a cone secured to a roof substrate by a linear fastener, a retainer cap with a conical hollow within resilient tines forming a slotted cylindrical wall snapped over the base cone and sandwiching the membrane between it and the base cone, the retainer cap being externally threaded and having an internally threaded cover thereon. This construction has been found to have a number of problems and potential problems associated with it. If the cover is screwed down too tightly onto the retainer cap, the membrane may become pinched between the tines of the retainer cap, and a tear in the membrane could result. The tear may not show up as a leak until snow, ice and rain conditions cause the water level on the roof to reach the tear in the membrane under the retainer cap of the membrane anchor. Also, if the cap is not tightened adequately, it may be easily removed by vandals, and used as a frisbee like toy; or the retainer and cover may possibly snap off as a result of wind uplift forces caused by high winds.
Anchoring systems in the United States are rated by insurance organization(s) for their resistance to wind uplift, that is, whether a particular roof construction will withstand wind forces of a specified amount. Rating categories typically used are I-30, I-60 and I-90, the construction being tested by placing, in the case of a membrane roof construction, a positive air pressure on the underside of the membrane and attachment constructions. For example, to achieve an I-90 rating, 90 pounds per square foot of pressure is thus applied, and the entire roof construction system must hold for a one minute period, at an initial pressure of 30 pounds per square foot, with the pressure increasing, in increments of 15 pounds per square foot, up to and including the 90 pound per square foot pressure. Each interval lasts for a similar one minute period of time. Architects, in designating particular roof constructions, take into consideration the maximum anticipated wind velocity in the geographic location where the roof is to be installed.
At present, point attachment single-ply roof anchoring systems have achieved a maximum of an I-60 rating with anchor constructions placed on three foot centers, that is, one anchor for evey nine square feet of membrane. Where the wind conditions in a particular section of the country require the maximum I-90 rating, the only presently approved membrane securement construction is by a strip attachment, or bar anchor, where a metal bar is placed over the edge of the membrane, spaced four feet apart, and the membrane being lapped, adhered, sealed and seamed. This requires, therefore a very time consuming and expensive construction for obtaining a satisfactory roof at locations where an I-90 rating is required. The ability to utilize non-penetrating fasteners which are more widely spaced is of material benefit. For example, considering a thousand square feet of membrane to be held in place, if the membrane anchors are placed on two foot centers, approximately 250 anchors are required; if the anchors are sufficiently strong that they may be placed on three foot centers, then the number of fasteners required for one thousand square feet is approximately 112. Where an anchor is capable of resisting wind forces so that it achieves a rating of I-90, when placed on four foot centers, only approximately 63 anchors are required. The dimination in the number of anchors, where a stronger anchor is utilized, results in markedly increased efficiencies both in cost of material and in labor costs.
A number of proposals have been made for construction of single-ply roof membrane anchoring systems which are of the non-penetrating type. Among these are that shown in Resan, U.S. Pat. No. 4,519,175, which is the widely used construction above discussed and is known to have a rating of I-60, with point attachment anchors as shown therein placed on three foot centers. Another disclosure of such an anchor system is Hahn, U.S. Pat. No. 4,502,256, a construction which includes in a single structural element a retainer cap, a clamp and a flexible disc extending downwardly and outwardly, formed from a metal spring plate which may be encased in a suitable elastomer or platomer material; the metal spring plate is annular, and is not capable of readily changing the internal diameter, which is necessary in order to provide a contracting socket for cooperation with the mushroom head of a base member.
Also of interest are Francovitch, U.S. Pat. No. 4,520,606, as showing various configurations of non-penetrating anchor systems, German Offenlegungsschrift No. 27 113 35 which provides an integral socket member in the form of an annulus, with an extension portion of small diameter, Offenlegungsschrift No. 28 26 969 which provides a resilient metal wire clamp directly engaging a membrane passed over the head of a base member, Offenlegungsschrift No. 23 39 901 which provides a socket member in the form of a rubber body, having a clamp on the exterior, and German Auslegeschrift No. 16 09 328 which provides a retainer cap in the form of a socket which engages with an undercut portion of a base member, with a membrane held thereby. Also to be noted is Offenlegungsschrift No. 22 33 714
The disclosures in the above-noted documents do not provide for secure systems of the non-penetrating type, which are simple to install, economical, and which would have great resistance to being disassembled by wind uplift forces on the membranes. A further defect in the above-noted constructions is that there is no provision to protect the anchor systems from the linear fasteners which hold the base plate from "backing out" as above described.